1. Technical Field
The present invention relates to a semiconductor device including a capacitive element and a method of manufacturing the semiconductor device.
2. Related Art
Capacitive elements are often incorporated in semiconductor devices. Since miniaturization of semiconductor devices has progressed in recent years, it has become necessary to increase the capacitance of the capacitive element without increasing the planar shape thereof. For example, Japanese Unexamined Patent Publication No. 2008-288408 and Japanese Unexamined Patent Publication No. 2007-158222 disclose that the capacitive element is formed in a three-dimensional type in order to increase the capacitance of the capacitive element.
In addition, in order to increase the capacitance of the capacitive element without increasing the area thereof, the thickness of the capacitive dielectric film may be reduced, or the relative permittivity of a capacitive dielectric film may be made high. However, when the thickness of the capacitive dielectric film is excessively reduced, the leakage current increases.
On the other hand, a technique of Japanese Unexamined Patent Publication No. 2008-288408 discloses that the dielectric constant of the dielectric film can be made high by adding Y or La to the dielectric film.
In addition, Japanese Unexamined Patent Publication No. 2007-158222 discloses that the capacitive dielectric film becomes amorphous by forming the upper layer of a lower electrode out of an amorphous titanium nitride film. According to Japanese Unexamined Patent Publication No. 2008-288408, it is possible to suppress the leakage current while making the relative permittivity of the capacitive dielectric film high by forming such a structure.
Meanwhile, Japanese Unexamined Patent Publication No. 2010-3742 discloses that the surface layer portion of a TiN film is made amorphous or microcrystalline in order to improve flatness of the TiN film which is a lower electrode of the capacitive element.
As mentioned above, in order to miniaturize the semiconductor device, it is necessary to increase the capacitance of the capacitive element without increasing the planar shape thereof. At this time, it is also necessary to suppress the increase in the leakage current of the capacitive element.